CDC Study Finds First Evidence That PrEP Can Reduce HIV Risk Among People Who Inject Drugs

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June 12, 2013


Dear Colleague:


Today, CDC, the Bangkok Metropolitan Association and the Thailand Ministry of Public Health, announced new results from a large clinical trial that provides the first evidence that a daily oral dose of an antiretroviral drug can reduce HIV transmission among injecting drug users (IDUs). The strategy of providing daily oral antiretroviral drugs to uninfected individuals prior to HIV exposure is called pre-exposure prophylaxis, or PrEP, and it has been previously shown to reduce HIV acquisition among men who have sex with men and heterosexual men and women.


The Bangkok Tenofovir Study found that a once-daily tablet containing tenofovir disoproxil fumarate (TDF) reduced the risk of acquiring HIV by 49 percent in this population. Similar to other PrEP studies, the trial also found that those who took the medication consistently had higher levels of protection.


Today's results represent an exciting step forward in the global fight against HIV. While other trials have shown that PrEP is safe and effective in preventing sexual transmission of HIV, these findings confirm that PrEP can prevent transmission of HIV through injection drug use as well.


Launched in June 2005, the trial enrolled more than 2,400 male and female IDU who were then randomly assigned to take either a daily TDF pill or a placebo. All participants in the study were provided HIV prevention counseling, a risk reduction package for both sexual and drug related risks, and monthly HIV testing.


Among the 1,204 participants taking TDF, there were 17 new HIV infections, compared with 33 infections among the 1,207 participants taking the placebo. Researchers also conducted an analysis to better understand the level of protection for those who adhered closely to the daily regimen. Among those known to be taking the study drug consistently, the risk of acquiring HIV was reduced by 74 percent compared to 49 percent overall – adding to the growing scientific evidence that high adherence to PrEP is critical to achieve the greatest benefit.


This trial also provided important information on risk behavior and drug resistance among participants. Trial participants in both arms reported decreases in their HIV risk behaviors, including injecting drugs, sharing needles and having sex with more than one partner. In addition, no TDF resistance was detected among participants who became infected with HIV during the trial.


Participants in the Thailand trial will now be offered access to TDF for HIV prevention for one year as part of a follow-on study which will provide additional data to help assess use and effectiveness outside of a trial setting.


More than 30 years into the epidemic, HIV remains a major health crisis. Worldwide, 2.7 million new infections are estimated to occur each year – including approximately 50,000 in the United States – and safe and effective new approaches to prevent HIV are urgently needed to reduce the toll of the disease. When used in combination with other proven HIV prevention methods, PrEP can play a role in helping reduce the number of new HIV infections in the United States and around the world.


In the United States, people who inject drugs represent 8 percent of new HIV infections and now account for roughly 10 percent of new HIV infections worldwide. In some regions of the world, such as Eastern Europe and Central Asia, this route of transmission accounts for up to 80 percent of new infections.

In the United States, key next steps will be consulting with clinicians, those who provide prevention services, and those who work with drug users to consider key implementation issues, including strategies to support adherence in less controlled settings, and the best settings for delivery of PrEP for people who inject drugs. CDC will begin working with federal partners like NIDA and SAMHSA—as well as state and local HIV prevention and substance abuse program partners to try to identify potential resources and settings in which these questions can be addressed.

In light of today's results, CDC has provided initial guidance for health care providers who may wish to prescribe PrEP to people who inject drugs. That guidance, published in today’s Morbidity and Mortality Weekly Report, recommends that providers who wish to prescribe PrEP for this population follow the same cautions and procedures in CDC’s existing interim clinical guidance on the use of PrEP to prevent sexual transmission. It also recommends key elements of prevention services for people who inject drugs and provides specific guidance on the antiretroviral drugs that should be considered for this population. CDC anticipates publishing more detailed Public Health Service clinical guidelines on PrEP use for both sexual and injecting drug risk later this year.

CDC is grateful to all of the trial volunteers who made this important research possible and have not only helped advance our understanding of HIV prevention among people who inject drugs, but have provided hope that many future infections can be prevented.

We are also grateful to you, our prevention partners, for the work you do every day in the fight against HIV.

The trial findings were published today in the Lancet.   

For more information on efforts to evaluate and plan for PrEP implementation in the United States, visit 


/Jonathan H. Mermin/ 
Jonathan H. Mermin M.D., M.P.H. 
Division of HIV/AIDS Prevention 
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention 

/Rima F. Khabbaz/
Rima F. Khabbaz, M.D.

Deputy Director for Infectious Diseases

Director, Office of Infectious Diseases

Acting Director, NCHHSTP

Centers for Disease Control and Prevention